Add support for collection keys in toObject.

docs/experiments/parsers/v4/example.js

@@ -40,7 +40,11 @@ const lines = [
   ` Further comments below. As I will now demonstrate, there is no simple`,
   `  even if embedded`,
   ` way of dealing with this problem.`,
-  ``
+  `author`,
+  ` name Second Person`,
+  ` email second@secondperson.com`,
+  ` More text,`,
+  ` across two lines.`,
 ]
 
 // Schema
@@ -76,7 +80,10 @@ async function main() {
     }),
     'scripts': () => toObject({ '#any': true }),
     'devDependencies': () => toObject(),
-    'author': () => toObject({ name: true, email: true, '#text': true })
+    'author': {
+      type: 'collection',
+      handle: () => toObject({ name: true, email: true, '#text': true })
+    }
   })
 
   console.dir(structure, { depth: null })